$-\dfrac{6}{8} + \dfrac{2}{12} = {?}$
Answer: $ = - {\dfrac{6 \times 3}{8 \times 3}} + {\dfrac{2 \times 2}{12 \times 2}} $ $ = - {\dfrac{18}{24}} + {\dfrac{4}{24}} $ $ = - \dfrac{{18} + {4}}{24} $ $ = -\dfrac{14}{24}$